Many applications, such as laser spectroscopy, optical pumping, and isotope separation, require a tunable narrow-linewidth source in the near infrared. Semiconductor lasers are an attractive alternative for these applications because of their relatively low cost, small size, and simplicity of operation. However, semiconductor lasers have had limited spectroscopic applications because of their inability to be tuned to arbitrary frequencies of interest within the laser gain curve. To alleviate this problem, several optical-feedback schemes have been devised that employ frequency-selective elements, such as gratings or etalons, in the feedback path. The most successful of these is discussed by Favre et al., who demonstrated continuous tuning of 15 nm with a linewidth of 20 kHz (deduced from beat spectrum). See F. Favre, D. LeGuen, J. C. Simon and B. Landousies, Electron, Lett. 22, 795 (1986). Others have also demonstrated the ability to tune (discontinuously) to arbitrary frequencies within the laser gain curve with linewidths of 100 kHz or less. Linewidth reduction without improved tuning characteristics has also been achieved by using nonfrequency-selective feedback. However, all the optical-feedback techniques that demonstrate the ability to tune to arbitrary laser frequencies require the use of modified anti-reflection coated lasers which are difficult to make and are thus very costly to purchase, and, in addition, are highly sensitive to alignment of the external optics. These factors detract from the simplicity and low cost inherent in semiconductor lasers.